1. Field of the Invention
The present invention relates to a method for joining non-woven fabrics. More particularly, it relates to a method for joining, via heat bonding, non-woven fabrics used for dust-proof working wear, etc.
2. Description of the Related Art
Generally, it is well known that non-woven fabrics have the characteristics of airtightness. Making the best use of this airtightness, non-woven fabrics have been utilized for a dust-proof or surgical working wear, etc.
It is well known that, when working wear is made by non-woven fabrics of such characteristics, they have been joined to each other with sewing thread. However, when the above joining method for joining non-woven fabrics is used, many holes are made in them owing to sewing thread. Consequently, since airtightness is lost, it is impossible to make the best use of the characteristics of non-woven fabrics by sewing them together.
A method as shown in FIG. 1A has been provided, according to which method non-woven fabrics may be joined to each other without sewing thread. In the method as shown in FIG. 1A, the end portions 100A and 100B of two non-woven fabrics 100 and 200 are made to be opposed and superimposed. The superimposed portions are bonded with heat while the width W thereof is kept constant.
Taking this means of heat bonding as an example, there is also known super-sonic wave welding as well.
Sewing thread is not used in the method as shown in FIG. 1A. Hence, the airtightness of non-woven fabric can be maximally utilized.
However, the problems of the above conventional method are as follows, regarding the manufacturing efficiency of the method and the joining strength of the product manufactured by the method.
First, the manufacturing efficiency is low.
In the conventional method as shown in FIG. 1A, the end portions 100A and 200A of two non-woven fabrics 100 and 200 are bonded with heat, by means of superimposing them by width W. However, it is very difficult to keep the width W fixed throughout all the processes. For example, though the size of the width W must be originally kept constant from the first position 1 to the final position 2 as shown in FIG. 1B, there are instances where the non-woven fabric 200 becomes askew with the non-woven fabric 100 during the processes, and accordingly, the size of the width W is not kept fixed. In this case, since the method must be restarted, all the processes until then go to waste. Hence, the conventional method has the problem that the manufacturing efficiency thereof is low.
Another deficiency of the conventional method is that the joining strength of the product is small. In the conventional method as shown in FIG. 1A, in side view, the joining place of the non-woven fabrics 100 and 200 is only at one place a. Accordingly, there is the problem that the joining strength against forces f1 and f2 in the transverse direction is weak, as shown in FIG. 1A. Hence, the non-woven fabrics 100 and 200, which are joined each other, are easily torn apart by the operation of the above forces f1 and f2. Consequently, the airtightness of non-woven fabrics is lost or difficult to maintain.